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if they are distributed exactly as the eigenfunction of the stationary problem. In the case of an arbitrary
external source, this number becomes:
⎛
µ src
= ν 1 ⎞
⎜ −1
⎟
⎝ k src ⎠
= ν
M src
−1
The ratio:
ϕ * = µ eff
= 1− k eff
µ src
1− k src
( )( k eff
ν)
( )( k src
ν)
is known as the importance of source neutrons. ν * is an effective number of neutrons per fission and
thus contains a correction for non-fission multiplicative processes such as (n,Xn) reactions, which are
of great importance for lead-bismuth or lead cooled fast reactors.
The neutronic properties of three different source cases has been examined: a spallation source
driven reference configuration (in short: reference or ADS case), a deuteron-deuteron fusion source
case (D-D or DD) and a deuteron-triton fusion source case (D-T or DT). As compared with the
reference case, the D-D configuration stayed within a range of 260 pcm (1 pcm = 1·10 -5 ) in terms of
the neutron multiplication factor (k src ), cf. Table 3. The D-T source configuration exhibits a
distinctively higher k src than the reference case, the difference in k src being 1 500 pcm (0.015). Other
central neutronic parameters are shown in Table 4. It should be noted that the required fusion source
intensities (“External n/s” in Table 4) are remarkably high. For comparison, it can be mentioned that
the source intensity of large-scale inertial confinement fusion experiments reaches a level of ~10 18 n/s
for the higher yielding D-T fusion.
Table 3. Neutron multiplication factors for the different source configurations
k eff
k src
ADS Fusion-DD Fusion-DT
0.9634 0.9640 0.9614 0.9790
Table 4. Main neutronic parameters for the different source configurations
ADS Fusion-DD Fusion-DT
ϕ* 1.0196 0.9478 1.7727
M = 1/(1-k src
) 27.8 25.9 47.6
Total n/s 8.01 10 18 7.98 10 18 8.13 10 18
External n/s 2.88 10 17 3.08 10 17 1.71 10 17
fiss/s 2.50 10 18 2.50 10 18 2.50 10 18
ν* 3.09 3.07 3.19
σ capt
(U 238 )/σ abs
(Pu 239 ) 0.68 0.68 0.68
Since the D-T source configuration case was found to show the most notable differences in
comparison with the reference ADS case, the onus will be on comparing the reference ADS and D-T
source configuration cases. In Table 5, the neutron balance of the whole EADF device is presented.
The fuel core neutron balance is presented in Table 6.
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